Punch assembly



Aug. 15, 1967 G. G. F. SMELTS 3,335,627

PUNCH ASSEMBLY Filed April 24, 1964 .FIG. 1.2

United States Patent 3,335,627 PUNCH ASSEMBLY Gerard Gaston Frans Smelts, Brampton, Ontario, Canada, assignor to Pierce-All Manufacturing Limited, Rexdale, Ontario, Canada Filed Apr. 24, 1964, Ser. No. 362,289 11 Claims. (Cl. 83-140) This invention relates to a punch assembly for use in the making of perforations in sheet metal or other materials. The punch assembly is suitable for use with punch press machine and is especially suitable for use with punch press machines utilizing a flexible punch-holder mechanism as described in Canadian Patent 655,761.

Known punch assemblies comprise a unitary punch and stripper spring arrangement cooperating with a punch guide which acts as the stripper as well. When it becomes necessary to change punch sizes the punch and stripper spring assembly plus the punch-guide-stripper must be changed. This results in costly down time for the press machine. In addition the overhead cost is great due to the fact that for every punch size there must be included a stripper spring and a punch-guide-stripper.

It is therefore an object of this invention to provide a punch assembly in which punches of various sizes may be employed without the necessity of providing individual stripper springs.

It is a further object of this invention to provide a punch assembly in which only the punch and a very inexpensive stripper need be changed to change size or shape of the hole being punched.

It is a still further object of this invention to provide a punch assembly in which only the punch and stripper need be changed while the facility for orientation of shape punches is maintained.

In accordance with this invention a punch holder comprises a shaft-like member provided with a punch head cavity into which the punch may be readily inserted and held rigidly with respect to longitudinal movement of the shaft member. A stripper spring is secured between the punch holding end of the shaft member and the other end so that it may be compressed by a further member which surrounds the punch holding end of the shaft and cooperates with or forms part of the punch guide. The further mcmber(s) comprises a pnnch-guide-stri-pper combination which may be of unitary structure but which for economy reasons is preferably of two parts, a punch guide member and a stripper insert.

In order to further clarify the description of the invention reference will now be made to the figures of the drawing in which FIGURE 1 is an exploded viewof a first embodiment of the invention utilizing a unitary guide-stripper,

FIGURE 2 is a view of the parts of FIGURE 1 in assembled relationship,

FIGURE 3 is an exploded view of a further embodiment of the invention in which the guide-stripper is made up of two parts, and

FIGURE 4 is an exploded view of a modification of the embodiment of the invention shown in FIGURE 3 where provision is made for secured punch orientations.

Referring now to FIGURE 1, a punch holder comprises a shaft 1 provided with a cylindrical punch head holder 4 having a portionof the wall of the cylinder removed so that the enlarged head 7 of a punch 6 may be inserted laterally into the internal slot provided therefor and held rigidly against longitudinal movement with respect to 1 and 4. A stripper spring 2 which may be a helical spring or consist of bowed washers is held, partially compressed, between cylindrical portion 4 and a ferrule 3 secured to the opposite end of shaft 1. A combination guide-stripper 8, provided with a large internal 3,335,627 Patented Aug. 15, 1967 diameter, is adapted to fit over punch 6 and bolder member 4 with the upper end of portion 9 abutting against the lower side of the stripper spring 2. The length of guide-stripper 8 is such as to allow the punch to be pushed through the stripper-guide and punch through a desired thickness of sheet material when the guide 8 is in position in a punch holder of a machine press and punching pressure is applied to the upper end of shaft 1. The lower portion of guide-stripper 8 is aperturcd to accept the workend of the punch 6 so that it may act as a stripper as well as guide.

When it becomes necessary to remove the punch and insert another this may be readily accomplished by lifting the punch clear of the guide and laterally removing the punch 6 from holder 4.

The guide-stripper may, if desired, be provided with an orientation key 10.

FIGURE 2 shows the punch guide-stripper assembly as it would appear assembled.

FIGURE 3 shows a further embodiment of the invention difiering from that shown in FIGURES l and 2 in that the guide stripper is composed of two separate pieces 11 and 15 wherein 11 is a stripper insert for punch guide 15. In this embodiment punch guide 15 is somewhat similar to the guide-stripper of FIGURE 1., 'but of large enough internal diameter to accept stripper insert 11. The lower portion of guide 15 is internally splined to accept the lower open cage portion of stripper insert 11 wholly within the splines 16 so that the machined innermost surface of the splined portion of guide 15 acts as the guide bearing surface for the punch 6. The stripper insert is provided with an enlarged diameter upper portion 14 and a cage-like lower portion comprising bars 13 parallel to the axis of the insert and which are integral with a flat platelike end portion 12 which acts as the actual stripping member. The insert is supplied with the plate 12 blank and when a punch such as shown at 6, with a reduced punch end 6a, is employed the punch produces its own, and consequently proper sized perforation in plate 12. Thereafter the punch and plate can be retained as a working unit although the insert could be used with punches having the same or larger punch end 6a. The punch can be used without a stripper when punching heavy and stiff sheets but for thin soft sheets a stripper is necessary.

In the embodiment shown in FIGURE 3, the punch guide 51 is used with a range of punch sizes up to one of a maximum cross-sectional dimension equal to the smallest internal transverse dimension of the splined portion of the guide. As a consequence, it is only necessary to have on hand one or a small number of guides to accommodate the punching of a large range of hole sizes which results in a substantial economy of inventory. In addition, the stripper insert, since it does not function as a guide, may be readily cast from steel resulting in further economy. The embodiment of the invention shown in FIGURE 4 is adapted for use in punching operations requiring special shapes and orientations of the holes to be punched. In this figure the punch guide 25 is similar to that of FIGURE 3 except for the milled key slots 26 in the upper end of the guide. The reasons for the slots will become evident as the description proceeds.

For punching shapes with particular orientation the punch 16 differs from that shown in FIGURES 1 or 3 in that the end portion 19 is contoured to provide a desired shape of hole, shown here as being rectangular. Additionally, at least one flat 17 is provided on the main body of the punch for control of angular orientation in cooperation with the stripper now to be described.

The stripper for pun-ch orientation preferably is made up of two parts 20 and 28, the lower cage-like part 20 having longitudinal bars 23, 24 integral with a stripper plate portion 21. At least one of the upper ends of bars 24 is provided with an inturned end portion 24a which, when the stripper is in position about punch 16, snaps into the depression produced by flat 17 and secures the stripper cage against accidental removal from the punch. The upper portion 28 of the stripper is in the form of an open sided cylinder having a lower end plate 29 cut away at 30 to receive the punch 16, when laterally inserted into the open side of the position 28 and cooperating with flat 17 to secure the punch against angular rotation with respect thereto. The stripper portion 28 is provided with keys or bosses 31 which cooperate with the key slots 26 in guide 25. The guide 25 may be provided with a key or the keys 31 may project beyond the outer surface of the guide 25, when assembled, to cooperate with milled keyway in a punch guide holder of a machine press to provide the desired orientation of the punch and punch guide with respect to the machine press work table.

In the punching operation of the assembly shown in FIGURE 4 the lower end of part 28 contacts at least two of the cage bars 23, 24 to provide the stripping pressure, it being understood that a punch holder, such as shown in FIGURE 1, is used with the assembly of FIG- URE 4 as well as that of FIGURE 3.

In order to allow assembly of the units of FIGURE 4 with the punch holder of FIGURE 1 the part cut away from the cylinder wall of upper position 28 must allow the part to be moved laterally onto the punch 16 and about the holder portion 4 when the punch is held in the holder. When the upper and lower parts of the stripper are assembled on a punch held in holder 4 lateral dislocation of the assembled parts is not possible as will be obvious. Thus the assembled unit may be readily removed from the guide as if in one piece thus providing for ease of punch changing. The lower cage portion 20 of the stripper will normally not be removed from the punch. If it is desired to change punch size and shape the assembled units are removed from the guide 25, the punch is removed laterally from the holder, the upper portion 28 of the stripper is removed axially from the holder and the new punch with its associated stripper is inserted in the holder and the parts re-assembled.

As will be observed now it is not normally necessary to exchange more than the punch and lower cage of the stripper to change hole size or shape. Here again the inventory for facilitating the punching of a range of hole sizes and shapes may be obtained from a stock of punch sizes and shapes, each with its associated stripper cage, and a minimal number of punch holders and guides.

It will be obvious that minor variations of the embodiments shown may be made with-out departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a punch assembly for perforating sheet material, an elongated punch holder provided with one end in the form of a short tube with one side cut away to allow the lateral insertion of a flanged head of a punch member, an internal annular groove in said tube cooperating with an inserted punch head to prevent longitudinal separation of said holder and punch, a stripper spring mounted in partially compressed condition between said tubular portion and the other end of said holder, a punch guide and stripper unit adapted to surround said tubular portion and an inserted punch and contact the stripper spring adjacent said tubular portion.

2. The assembly as claimed in claim 1 wherein the guide and stripper unit comprises two parts, an external guide and an internal stripper wherein the stripper has an active stripper plate supported by a plurality of bars extending parallel to the punch and accommodated in internal splines provided therefor in said guide part.

3. An assembly comprising an elongated body punch member having a flanged head adapted for lateral insertion into a hollow tubular punch holder provided with a side opening, a stripper member provided with an active stripper plate supported at its edge by a plurality of spaced parallel bars extending orthogonally to the flat surface of said plate closely surrounding the working end of said punch member and terminating at an enlarged tubular member surrounding the flanged head of said punch, said enlarged member providing the mechanical connection between the stripper and a stripper spring during punching operation.

4. An assembly as claimed in claim 3 wherein said parallel bars are integral with said enlarged member.

5. An assembly as claimed in claim 3 wherein said enlarged member is provided with a side opening and internal flats which cooperate with flats provided on the body of the punch to prevent relative angular movement of said enlarged member with respect to said punch, and external boss means on said enlarged member adapted to cooperate with an orientation key slot of a punch guide.

6. A punch and guide assembly comprising an elongated body punch provided with a flanged head for lateral insertion in a tubular punch holding member having an internal groove for cooperation with said flanged head to prevent longitudinal separation of an inserted punch from said holder, a stripper plate supported at its edge by a plurality of parallel bars extending orthogonally with respect to the flat surface of said plate and adapted to surround the working end of said punch, a tubular member having an opening in the side thereof to accommodate lateral insertion of the punch and act as a pressure coupling member between said parallel bars and a stripper spring associated with said punch holding member, a hollow guide member provided with an enlarged end adapted to surround said tubular member and a smaller end adapted to accommodate said bars wholly within internal spline grooves.

7. The assembly as claimed in claim 6 wherein said tubular member is provided with internal flanges cooperating with flats provided on the body of said punch to prevent relative angular rotation between said tubular member and said punch, and means preventing relative rotation between the tubular member and said guide member.

8. The assembly as claimed in claim 7 wherein at least one of said bars is provided with an inturned flange which in cooperation with one of said flats prevents inadvertent removal of said stripper from said punch.

9. A stripper, for use with a punch guide provided with internal spline grooves comprising a flat stripper plate provided with a plurality of spaced support members each attached at one end to the edge of said plate and extending orthogonally with respect to one surface of said plate thereto and wherein the supports are wholly accommodated within the spline groove when said stripper is inserted into a splined guide adapted therefor.

10. The stripper as claimed in claim 9 wherein at least one of said supports is provided with an inturned flange at its other end, which flange cooperates with a flat when assembled on a punch provided with at least one flat, to prevent inadvertent axial removal of said stripper from said punch.

11. The stripper as claimed in claim 9 wherein it comprises a tubular end portion, opposite to said plate, which surrounds the head of a punch, when in assembled working arrangement to provide a mechanical force connector between a stripper spring and said support members.

References Cited UNITED STATES PATENTS 1,151,032 8/1915 Moore 83588 X 2,108,619 2/1938 Smith 83-140 X 2,191,836 2/1940 Stromberg et al. 83-140 X 2,808,108 10/1957 Pellegrino 83700 X WILLIAM W. DYER, JR., Primary Examiner. JAMES M. MEISTER, Examiner.

F. T. YOST, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,335 ,627 August 15 1967 Gerard Gaston Frans Smeets It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the sheet of drawings, line 1, for

"G. G. F. SMELTS" read G. G. F. SMEBTS in the heading to the printed specification, line 3, for "Gerard Gaston Frans Smelts" read Gerard Gaston Frans Smeets Signed and sealed this 19th day of November 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr.

EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN A PUNCH ASSEMBLY FOR PERFORATING SHEET MATERIAL, AN ELONGATED PUNCH HOLDER PROVIDED WITH ONE END IN THE FORM OF A SHORT TUBE WITH ONE SIDE CUT AWAY TO ALLOW THE LATERAL INSERTION OF A FLANGED HEAD OF A PUNCH MEMBER, AN INTERNAL ANNULAR GROOVE IN SAID TUBE COOPERATING WITH AN INSERTED PUNCH HEAD TO PREVENT LONGITUDINAL SEPARATION OF SAID HOLDER AND PUNCH, A STRIPPER SPRING MOUNTED IN PARTIALLY COMPRESSED CONDITION BETWEEN SAID TUBULAR PORTION AND THE OTHER END OF SAID HOLDER, A PUNCH GUIDE AND STRIPPER UNIT ADAPTED TO SURROUND SAID TUBULAR PORTION AND AN INSERTED PUNCH AND CONTACT THE STRIPPER ADJACENT SAID TUBULAR PORTION. 